AnimalCrackers

Hey! So I'm still really new to working on cars especially the rx8, I've gotten as far as to finally getting the car to try and start from previously it not attempting to do so, but now im stuck at getting the car to try and start but when its trying to start theres a consistent knocking sound coming from somewhere under the car, from what im aware the engine has low compression, so im wondering if it could be a broken seal or bearing? I've attached a short video of what the knock sounds like from inside the car if its any help, and I can get more recording of the knock if needed, thanks!

BigCajun

iTrader: (1)

I don't hear a knock, but it sounds like it's flooded or blown and not turning over fast enough to start.

AnimalCrackers

It sounds more like a consistent rotational punch I guess? I imagine its probably blown apex seals considering the person I bought it from says it had low compression, but what should I do if the engine is flooded as you say it could be? And the starter had already been replaced, but if its not turning over fast enough is a new starter something I should look into?

BigCajun

iTrader: (1)

It's been my experience that if a battery is not strong it likely will not start a flooded engine.
A healthy engine usually floods only if the battery accidentally gets drained.
My last 2 tested 'good' but it wouldn't start until I put in a new battery.
Both were less than 3 years old.

The telltale sign for me is if the cranking rpm noticeably slows after several tries.
If this happens and you plan on keeping it, a new battery might be worth the risk.

There are multiple flooding threads, I pull the fuel pump fuse.
It can be a tricky procedure.

A reasonably healthy engine will start after a few tries, one with bad compression can take a long time.
Some people pull and dry the plugs and crank the excess fuel out, I've never tried it.
It might be necessary for an engine with really bad compression issues.

https://www.rx8club.com/series-i-do-...lumber-182410/

Loki

iTrader: (1)

I don't hear a knock either, but it doesn't sound abnormal, just a bit slow. As above, make sure the battery is well charged and in good shape. Battery terminals too.

Pull the spark plugs and see what they tell you about the last time it ran, and if flooded clean them off and do a thorough deflooding. Could be that simple.

Since the car is new to you, you'll want to verify ignition, compression, cooling health, etc.

AnimalCrackers

This has given me a lot more to consider! The battery has already been replaced with a Duralast Gold, but it sounds like it definitely could be flooded considering when I bought the car the battery had been bought used and barely even kept the lights on in the car let alone let the car turn over, with the fuel pump fuse being not present, so the previous owner might have been in the process of deflooding the car himself? Im not entirely sure but there's no harm in trying the process again.

The battery will probably need to be charged, but ill check the spark plugs and ignition coils too, I was told they were replaced prior to me buying the car.

For the knock or bump that must just be me worrying about something hopefully normal? it just seemed a little loud (especially in person) and I could almost feel it bumping when sitting in the car but that might be due to slow cranking rpm like said before.

BluSpectre

Those little "Thwump Thwump" sounds in a 1-2 fashion are the rotor faces opening up on the exhaust port. This is perfectly normal operation, and means your engine has compression. As for how good, IDK. A proper test is required for that. The turn over speed does sound low though.

JoeBlow

What does ; the fuel pump fuse not being present; mean?

AnimalCrackers

Thank you for explaining the Thwumping sound i'm glad to know it actually is normal lol.

and for the fuel pump fuse being removed, I think it was due to the previous owner trying to start the process of deflooding the engine.

MincVinyl

How cold was the ambient temp?
Which starter was the original replaced with? the upgraded 2.7hp version?

That knock/thump sounds like normal slow engine spinning. Slow starting could be low CCA battery or a dead battery or both. Or the starter could be bad or the slower starter or both. Try to take the sparkplugs out without spinning the engine much more. You will want to know if they are wet and either smell like fuel/ oil/ coolant(sweet). Fuel likely points to poor starter/ battery/ ignition/ compression. Oil points to bad oil rings/ OMP/ Oil injectors. Coolant points to blown coolant seals, which will lead to buying a reman engine.

All that being said, I had similar symptoms on the 3rd rx8 I just bought that was at 80k miles with a half dead battery and the oem starter. Was fine after a charge and throwing on my spare 2.7hp starter(80$ or so on amazon if I remember correctly). Had to poor mans deflood and throw a clean set of plugs on from my stash.
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The poor mans way of deflooding the car is to hold the gas pedal to the floor and then hold the key on ignition/start for 7 or so seconds. Holding your foot to the floor will cut fuel but not spark, you would do this 5-7 times with breaks in between to not burn up your starter. I always leave the bad set of plugs in when doing this type of deflood method. This isnt as thorough as the full deflood procedure since this rotary engine has side exhaust ports, which means the flooded liquid has to make two 90deg turns out of the engine. The full deflood procedure has people take the spark plugs out since the plug holes are inline with the center of the apex seals, I believe the procedure cuts spark since the plugs come out.

When I had blown coolant seals I had to poor mans deflood just about every time I wanted to run my car. Went through plugs like nobody's business, but got me through college.

Loki

iTrader: (1)

Is your engine actually turning? If you have someone watch the belts at the front of the engine while you crank, do they move?
Because on second listen it sounds like the starter is turning, but it might not be engaging the flywheel.

AnimalCrackers

Im not sure about the temp or replaced starter, id need to get under the car and check which ill be doing tomorrow since I finally have free time to do so, but with the previous owner buying a used and mostly dead battery I wouldn't be surprised if this is a used OEM starter. But after hearing a lot about the related symptoms im definitely going to be trying the deflooding process to see if I can get higher starting rpms and hopefully finally being able to start the car. I haven't pulled the spark plugs yet but again I will be doing so tomorrow so ill keep this thread updated probably later in the day.

Also to respond to the engine turning yes the belts on the front move, or they should be moving as the last time I tried to turn over the car both belts moved, I actually had to set up my phone with a flashlight to check lol, I can triple check again tomorrow morning.

Ill also look into either trying to "poor man" deflood the engine or go through that whole process of deflooding it, which I read through a bit but dont fully understand yet so I have my research ahead of me! Thanks for all the information again though this has been insanely helpful.

AnimalCrackers

Alright so I've been trying to go through the process of deflooding the car, spent about an hour trying it and not much has changed, I had another car jump my car and stay running while connected to my battery so there should be no issue there, I haven't gotten a chance to get under the car and check out both the starter and the spark plugs, the only main new thing is that there's a loud tick sound which can be heard in the attached video of me trying to turn the car over, no clue if its normal but it sure is there so I wanted to double check:

Loki

iTrader: (1)

Are you sure there isn't a spark plug missing? The chuff-chuff-chuff sounds like compression escaping somewhere, like if a plug had come out. Are you getting a fuel smell after deflooding for a bit?

BigCajun

iTrader: (1)

Still sounds flooded or a blown engine to me, and not turning fast enough.
Even jumping it might not give you enough power.

If you plan on keeping the car no matter what and can afford a new battery, try it just to eliminate that possibility.

I have a battery charger/booster that couldn't get mine started recently and it wore out the AAA guy's booster pack trying to start it with a 1 year old battery.
It tested 'good' so I couldn't get the warranty but this was the second time I had a 'good' battery replaced.

It took a new one to get it started.
I even got it started before the guy left.
He just shook his head.

BigCajun

iTrader: (1)

Good point.
The ceramics have been known to separate also.
A HEI tester would be a good idea to test the ignition system to rule out bad plugs or coils.
Even coils out of the box have been known to be defective

AnimalCrackers

I am getting a fuel smell yes, main reason I cant check the spark plugs yet is cause the drivers side is facing a wall and stuff is in the way (doing this all in a very small garage) but I can try and slide all the way from the opposite side of the car and check if all plugs are there, I have been told coils + plugs had all been replaced but maybe they were faulty?

Also for the battery I bought it new for the car not even a month ago, its a Duralast Gold, specifically bought it hoping it would last a decent while, I have only been connecting the battery off an on for a little bit while messing around with the car but would that be enough to immediately kill it? it could be the terminals themselves? They look pretty beat up and it might be worth just buying outright new ones at this point.

BigCajun

iTrader: (1)

The batteey should be good then.
Unless it died completely, every time a battery gets drained it gets weaker.

AnimalCrackers

Alright so I got under the car and sure enough there's a spark plug missing lol, its the second leading spark plug, I can't find the right spark plug wire for it either which is strange considering they are all brand new so I have no idea what the previous owner did with both the plug or wire? He even gave me a box of old parts which have the OEM wires so I find that strange.

I imagine having basically a hole in the engine would cause just a bit of a problem yeah?

Edit: I found the wire it was just hidden up in the engine itself, still doesn't explain the plug though, would he have taken it out for deflooding purposes maybe?

Loki

iTrader: (1)

Well dere's yer problem.
May want to verify that the other plugs are actually in the right places (trailing and leading used in correct positions). Who knows what else he goofed up.

AnimalCrackers

I definitely will verify that tomorrow when I pick up the missing leading plug lol, ill keep this thread updated after I install the new plug and try to start the car again.

AnimalCrackers

So I've replaced the missing Leading plug, and also am very glad Loki recommended checking cause the dude who I bought it from had a second leading plug where a trailing plug should be, no clue how that got messed up, but I went back out and bought a trailing one, put it in, and then had to switch batteries cause my other battery was dead (new one has 600 cold starting amps if that matters, previous had 800) but I hoped for the best and went through the process of trying to deflood the engine and still had no luck.


Should I try and remove the spark plugs and deflood the engine again? Or is there any worth looking into replacing the starter? Im at a loss, it also doesn't sound normal when comparing to other rx8 starts but would that be due to it still being too slow?

AnimalCrackers

I've been looking more into it, would the engine itself be misfiring when trying to start and that's why I think it sounds wrong? I have a feeling something really small isn't installed right like the wires to the actual plugs (mostly cause looking at all the previous things the owner had messed up on the car I'm worried)

I'm gonna try and mark the wires and take them all off then go through the process of reconnecting them to see if that changes anything.

Loki

iTrader: (1)

Proper coil and spark order is always good.
Honestly it sounds fine now. Is the tachometer moving at all when you try to crank? It doesn't look like it. Is your eccentric shaft sensor connected? Really need that and PO might have unplugged it while trying to deflood.

MincVinyl

Would agree with Loki,

no tach would point towards the computer doesn't know what the timing is. Doesn't sound like it is spinning slow enough that the tach wouldn't move. Check that the E-shaft sensor is plugged in. Make sure it is clean, could even clean the plug if you want. Might as well try to wiggle the battery terminals. At this point anything the previous owner did was likely wrong and I would consider any bolt they may have touched not tightened so to speak. Then make sure you do the 20 brake stomps again.

Otherwise sounds like a normal slow spinning poorly maintained rx8. Sadly there are many threads where new owners have to take on the burden of a previous owner that ran everything on the car into the dirt.